1. Field of the Invention
The present invention relates to display systems. More specifically, the present invention relates to helmet mounted displays.
While the present invention is described herein with reference to illustrative embodiments for particular applications, it should be understood that the invention is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, and embodiments within the scope thereof and additional fields in which the present invention would be of significant utility.
2. Description of the Related Art
Helmet mounted displays are useful in simulator, entertainment and virtual reality applications. Helmet mounted displays include a projector which provides an image on a screen or window which is attached to a helmet. As the head of the wearer moves, the displays moves and maintains an image in the field of view of the wearer. In displays in which the projector is bulky and heavy, the projector is mounted off the helmet and the image is relayed to the screen by a fiber optic cable and relay optics. To recreate the image with acceptable resolution, the fiber optic cable includes a large number of individual fibers which are often arranged into 5 by 5 arrays or multifibers.
Unfortunately, it is common for several multifibers to break creating dead spots in the display obscuring the displayed image.
One prior approach to this problem involves the use of a prism at the input end of the image guide to spread the color spectrum of the image over many fibers. An identical prism installed at the output end served to recombine the color spectrum into a single image. Unfortunately, this approach would not work in laser based projectors because the primary colors are single wavelengths. As there is no broad color spectrum with these systems, all energy for each color would pass through a single fiber only.
Another approach involves the use of tilted flat glass plate, one at the input and one at the output end. The plates are spun synchronously to spread the image in a circular pattern over many fibers. This approach would also be ineffective with laser projectors as laser light has zero persistence. Every point in the image is illuminated for just an instant. The stroboscopic effect of the scanning laser beam is such that the illumination of each point passes only through a single fiber.
Hence, these incoherent techniques for minimizing the effect of dead fibers in fiber optic image guides do not adequately address the problem of dead fibers in the otherwise advantageous laser projector.
Accordingly, there is a need in the art for a technique for correcting for dead spots projected images resulting from broken fibers in laser projector based helmet mounted displays.